A cupcake is NOT a muffin my friend. There is a distinct difference!! A cupcake is a cake baked in a cup. However, it is not just cake in a cup; If I were to stuff a slice of cake into a coffee cup that wouldn't make it a cupcake. That would make it a slice of cake in a coffee cup.
The real question is not what is a cupcake, it is what is a muffin?! Is a muffin a fin in a muff?!?

Cherry baked cupcakes by pouring the batter into little cups and baking them in the oven.
It tasted like a cake, not a muffin, so she put frosting on it.